For hearing aid users, certain physical activities induce low-frequency vibrations that excite the hearing aid microphone in such a way that the low frequencies are amplified by the signal processing circuitry thereby causing excessive buildup of unnatural sound pressure within the residual ear-canal air volume. The hearing aid industry has adapted the term “ampclusion” for these phenomena as noted in “Ampclusion Management 101: Understanding Variables” The Hearing Review, pp. 22-32, August (2002) and “Ampclusion Management 102: A 5-step Protocol” The Hearing Review, pp. 34-43, September (2002), both authored by F. Kuk and C. Ludvigsen. In general, ampclusion can be caused by such activities as chewing or heavy footfall motion during walking or running These activities induce structural vibrations within the user's body. Another user activity that can cause amplusion is simple speech, particularly the vowel sounds of [i] as in piece and [u] is as in rule and annunciated according to the International Phonetic Alphabet. Yet another activity is automobile motion or acceleration, which is commonly perceived as excessive rumble by passengers wearing hearing aids. Automobile motion is unique from the previously-mentioned activities in that its effect, i.e., the rumble, is generally produced by acoustical energy propagating from the engine of the automobile to the microphone of the hearing aid. Thus, there is a need in the art for a detection scheme that can reliably identify user activities and trigger the signal processing algorithms and circuitry to process, filter, and equalize their signal so as to mitigate the undesired effects of ampclusion and other user activities. Such a detection scheme should be computationally efficient, consume low power, require small physical space, and be readily reproducible for cost-effective production assembly.